When substances change from one solid phase into another the change is accompanied by absorption or release of heat. The temperature at which such a change takes place is called the transition temperature. This change can be thought of as a change from one compound to another. In this experiment, the compound used is Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20). Hydrates are formed when ionic compounds are formed in water and then isolated as solids, therefore the water remains trapped in the compound. Hydrates are written with a dot between the ionic compound and the amount of water molecules involved with the compound. This indicates the number of water molecules per one molecule of the ionic compound. Though water is involved in the chemical formula, this does not indicate that the substance is wet. In fact, many hydrates have dry appearance and touch. When water is removed from the hydrates, one is left with the anhydrous compound (dehydrate). When these hydrates are heated (change in temperature), the water will evaporate and thus the compounds will no longer be hydrates. When water vapour is added to the dehydrates, the dehydrates absorb the water vapour to form a hydrate.
In this experiment, an attempt will be made to find the transition temperature of a specific compound: Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20).
A variety of methods can be used to determine the transition temperatures of salt hydrates. The basis of the method used in this experiment is that the temperature will rise constantly until the hydrate evaporates, thus changing state. Thus, on heating crystals of Na2S2O3 . H2O, the temperature should rise normally until the hydrate begins to change into an anhydrous salt (i.e. water evaporates). Then the temperature remains constant until the transformation is complete. If the reverse change is allowed to take place, there is an evolution of heat. The temperature will fall at a definite rate until the transition point is reached. Then the temperature stays constant until all of the substance has been transformed. Therefore, by plotting a time vs. temperature curve, the transition point can be determined. When cooling the hot solution in an undisturbed manner, super cooling usually occurs below the transition point, and after falling 4 or 5 degrees C, the temperature of the compound suddenly rises causing crystallization, thereby providing an accurate transition point.
For this experiment, the compound will be placed in a test tube, which in turn will be placed in a large beaker filled with water. An air jacket (a container placed on top of test tube to prevent outside air flow) will be used while cooling the compound. A single crystal of Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20) will be added, and will act as a seed crystal. Seed crystals are used to expedite the crystallization of the compound as they eliminate the need for random molecular collision/interaction. By introducing an already pre-formed basis of the target crystal to act upon, the intermolecular interactions are formed much more easily than relying on random flow.
Materials
Retort stand
Ring clamp
Wire gauze
Bunsen burner
Flint lighter
Beaker tongs
Thermometer
Boiling tube
20 mL of Sodium Thiosulphate Pentahydrate
Electronic scale
150 mL of water
Temperature Probe
Computer
Scoopula
1 L beaker
Safety goggles
Procedure
1) Wear safety goggles
2) Set up a retort stand and clamp a ring clamp 30 cm above the base.
3) Set up a temperature probe attatched to a computer
4) Place a piece of wire gauze on the ring clamp so that the wire gauze fully covers the clamp.
5) Place a Bunsen burner beneath the clamp.
6) Place 100 mL of water into a 250 mL beaker and place the beaker onto the wire gauze until stable
7) Place a sensitive thermometer along with a temperature probe into the boiling tube
8) Place 50 mL of Sodium Thiosulphate Pentahydrate into a boiling tube
9) Place the boiling tube into the beaker
11) Record the compund's physical properties of weight, colour and other noticeable observations at the certain temperature. Mass will be measure with the use of an electronic scale
12) Ignite the Bunsen burner with a flint lighter and adjust to a moderate flame.
13) Start recording data with use of the temperature probe
14) When the substance melts, carefully remove the boiling tube using boiling tube clamps and place it into an air jacket
15) When the temperature drops to 40 degrees C, add one crystal of sodium thiosulphate pentahydrate and stir carefully
16) The temperature will increase suddenly and once the temperature remains constant, stop the recording of the data
17) Empty the contents of the beaker safely and wash the beaker.
Observations
The following table displays the relationship between time and temperature of sodium triosulphate pentaphydrate over the period of 30 minutes – 0 to 1800 seconds. The time is shown at 30 second intervals. The table also displays the occurring procedural steps. Data in blue is mathematically approximated. Relationship Between Time (s) and Temperature (˚C) Between 0s and 1800s
Time (s)
Temperature (˚C)
Procedural Step
0
21.1
Initial Temperature
30
20.9
60
21.9
90
24.5
120
29.9
150
44.7
180
50
210
55.9
240
68.6
270
67
300
73
At 294s, all of the substance has become liquid. Substance is let to heat for to an additional 5˚C
330
65.6
Temperature peaks at 73.8˚C having risen another 5˚C. Heat is turned off. Boiling tube is placed in an air jacket. Substance begins to cool.
360
64.3
390
64.8
420
63.3
450
62.4
480
61
510
60.1
540
58.4
570
56.8
600
56.2
630
55.3
660
54.7
690
53.8
720
53.1
750
52.2
780
51.4
810
50.8
840
50
870
49
900
48.2
930
47.5
960
46.8
990
46
1020
45.5
1050
45
1080
44.2
1110
43.5
1140
43.1
1170
42.4
1200
41.8
1230
41.1
1260
40.8
1290
40.3
The substance reaches 40˚C at 1294s. One crystal of sodium thiosulpahte pentahydrate is added to the boiling tube
1320
42.7
1350
47.2
As the temperature begins to stabilize, 47.6˚C is the transition temperature.
1380
47.9
1410
48.2
1440
47.9
1470
47.9
1500
47.8
1530
47.7
1560
47.7
1590
47.6
1620
47.8
1650
47.6
1680
47.8
1710
47.7
1740
47.6
1770
47.6
1800
47.6
For a greater understanding, below is a table displaying the temperature, recorded at 30 second intervals, of sodium thiosulphate pentahydrate after the heat was turned off. At time 331, the heat was turned off and the boiling tube was placed in an air jacket. Once the temperature reached 40˚C, one crystal of sodium thiosulpahte pentahydrate was added.
Relationship Between Time (s) and Temperature (˚C) After Heat Was Turned Off (311s - 1781s)
Time (s)
Temperature (˚C)
311
73.8
341
65.1
371
63.7
401
64.2
431
63.1
461
61.9
491
60.6
521
59.5
551
57.7
581
56.5
611
55.7
641
55.1
671
54.4
701
53.5
731
52.7
761
51.8
791
51.1
821
50.2
851
49.5
881
48.7
911
47.9
941
47
971
46.6
1001
46
1031
45.1
1061
44.7
1091
43.9
1121
43.6
1151
42.8
1181
42.1
1211
41.6
1241
41.1
1271
40.7
1301
40
1331
44.3
1361
47.7
1391
48.1
1421
47.9
1451
48.1
1481
47.9
1511
47.9
1541
47.9
1571
47.8
1601
47.8
1631
47.8
1661
47.8
1691
47.6
1721
47.6
1751
47.6
1781
47.7
Calculations
Below is the plotted graph displaying the visual relationship between time (s) and temperature (˚C). The full duration of the experiment is shown.
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The following graph visually represents the relationship between time and temperature during the time period of 311s-1781s at intervals of 30 s. During this time period, the heat is turned off at 311s and a crystal is added at 1294 s.
1) What is the significance of adding one crystal of Sodium Thiosulphate Pentahydrate at the end?
The single crystal of sodium thiosulphate acts as a seed crystal and speeds up the crystallization process. (add on)
2) Judging from the experiment, what information does the transition temperature of a compound provide?
3) Was this reaction endothermic or exothermic? How do you know?
4) What are some practical uses of transition temperature?
Sources of Error
In determining the transition temperature of hydrates such as sodium thiosulphate pentahydrate, knowledge of experimental errors are important, they can lead to inaccurate results.
Sources of experimental include faulty equipment such as the temperature probes. The results from the experiment were staggered due to the capabilities of the program "Logger PRO" which only allowed five minute time allocations and in result, approximately 29 seconds between each time interval was lost. There was some infromation lost in the transportation time in transferring the boiling tube from the clamp into the air jacket. Since the test tube was heated, it was slowly handled with caution. The lost information was obtained by simple mathematical calculations and averaged on the trends. Due to human error, there was no way to tell accurately when the sodium thiosulphate pentahydrate has tranformed fully into a liquified state. It was judged by vision and it could have been incorrect. Contamination could have occured in any of the materials used in the experiment such as the beakers, the scoopula, or the sodium thiosulphate pentahydrate.
we didn't take note of the temperature cause we used a computer
we used a temperature probe
yes. we did wait an extra 5 degrees i made a mistake on the excel sheet
explain what the air jacket is
200 OR 150 ml of water i need to check
we used a 250 mL beaker....
observations/data/calculations (I'm doing this part. DID YOU KNOW WE HAVE 30 MINUTES OF DATA?)
error (some i thought of)
the computer program could only have graphs up to five minutes so there was a lag between each graph approx 29 seconds each...as a result those results we obtained through simple math and averages....
time lag of transferring to air jacker
hard to deteremine if all of the sodium thiosulpahte had liquified (this might be human. hm unsure)
thermoter only had to .1 decimal. not very accurate.
Introduction
Table of Contents
When substances change from one solid phase into another the change is accompanied by absorption or release of heat. The temperature at which such a change takes place is called the transition temperature. This change can be thought of as a change from one compound to another. In this experiment, the compound used is Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20). Hydrates are formed when ionic compounds are formed in water and then isolated as solids, therefore the water remains trapped in the compound. Hydrates are written with a dot between the ionic compound and the amount of water molecules involved with the compound. This indicates the number of water molecules per one molecule of the ionic compound. Though water is involved in the chemical formula, this does not indicate that the substance is wet. In fact, many hydrates have dry appearance and touch. When water is removed from the hydrates, one is left with the anhydrous compound (dehydrate). When these hydrates are heated (change in temperature), the water will evaporate and thus the compounds will no longer be hydrates. When water vapour is added to the dehydrates, the dehydrates absorb the water vapour to form a hydrate.
In this experiment, an attempt will be made to find the transition temperature of a specific compound: Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20).
A variety of methods can be used to determine the transition temperatures of salt hydrates. The basis of the method used in this experiment is that the temperature will rise constantly until the hydrate evaporates, thus changing state. Thus, on heating crystals of Na2S2O3 . H2O, the temperature should rise normally until the hydrate begins to change into an anhydrous salt (i.e. water evaporates). Then the temperature remains constant until the transformation is complete. If the reverse change is allowed to take place, there is an evolution of heat. The temperature will fall at a definite rate until the transition point is reached. Then the temperature stays constant until all of the substance has been transformed. Therefore, by plotting a time vs. temperature curve, the transition point can be determined. When cooling the hot solution in an undisturbed manner, super cooling usually occurs below the transition point, and after falling 4 or 5 degrees C, the temperature of the compound suddenly rises causing crystallization, thereby providing an accurate transition point.
For this experiment, the compound will be placed in a test tube, which in turn will be placed in a large beaker filled with water. An air jacket (a container placed on top of test tube to prevent outside air flow) will be used while cooling the compound. A single crystal of Sodium Thiosulphate Penta Hydrate (Na2S2O3∙5H20) will be added, and will act as a seed crystal. Seed crystals are used to expedite the crystallization of the compound as they eliminate the need for random molecular collision/interaction. By introducing an already pre-formed basis of the target crystal to act upon, the intermolecular interactions are formed much more easily than relying on random flow.
Materials
Procedure
1) Wear safety goggles
2) Set up a retort stand and clamp a ring clamp 30 cm above the base.
3) Set up a temperature probe attatched to a computer
4) Place a piece of wire gauze on the ring clamp so that the wire gauze fully covers the clamp.
5) Place a Bunsen burner beneath the clamp.
6) Place 100 mL of water into a 250 mL beaker and place the beaker onto the wire gauze until stable
7) Place a sensitive thermometer along with a temperature probe into the boiling tube
8) Place 50 mL of Sodium Thiosulphate Pentahydrate into a boiling tube
9) Place the boiling tube into the beaker
11) Record the compund's physical properties of weight, colour and other noticeable observations at the certain temperature. Mass will be measure with the use of an electronic scale
12) Ignite the Bunsen burner with a flint lighter and adjust to a moderate flame.
13) Start recording data with use of the temperature probe
14) When the substance melts, carefully remove the boiling tube using boiling tube clamps and place it into an air jacket
15) When the temperature drops to 40 degrees C, add one crystal of sodium thiosulphate pentahydrate and stir carefully
16) The temperature will increase suddenly and once the temperature remains constant, stop the recording of the data
17) Empty the contents of the beaker safely and wash the beaker.
Observations
The following table displays the relationship between time and temperature of sodium triosulphate pentaphydrate over the period of 30 minutes – 0 to 1800 seconds. The time is shown at 30 second intervals. The table also displays the occurring procedural steps.
Data in blue is mathematically approximated.
Relationship Between Time (s) and Temperature (˚C) Between 0s and 1800s
Relationship Between Time (s) and Temperature (˚C) After Heat Was Turned Off (311s - 1781s)
Calculations
Below is the plotted graph displaying the visual relationship between time (s) and temperature (˚C). The full duration of the experiment is shown.The following graph visually represents the relationship between time and temperature during the time period of 311s-1781s at intervals of 30 s. During this time period, the heat is turned off at 311s and a crystal is added at 1294 s.
Conclusion
Discussion
1) What is the significance of adding one crystal of Sodium Thiosulphate Pentahydrate at the end?
The single crystal of sodium thiosulphate acts as a seed crystal and speeds up the crystallization process. (add on)
2) Judging from the experiment, what information does the transition temperature of a compound provide?
3) Was this reaction endothermic or exothermic? How do you know?
4) What are some practical uses of transition temperature?
Sources of Error
In determining the transition temperature of hydrates such as sodium thiosulphate pentahydrate, knowledge of experimental errors are important, they can lead to inaccurate results.
Sources of experimental include faulty equipment such as the temperature probes. The results from the experiment were staggered due to the capabilities of the program "Logger PRO" which only allowed five minute time allocations and in result, approximately 29 seconds between each time interval was lost. There was some infromation lost in the transportation time in transferring the boiling tube from the clamp into the air jacket. Since the test tube was heated, it was slowly handled with caution. The lost information was obtained by simple mathematical calculations and averaged on the trends. Due to human error, there was no way to tell accurately when the sodium thiosulphate pentahydrate has tranformed fully into a liquified state. It was judged by vision and it could have been incorrect. Contamination could have occured in any of the materials used in the experiment such as the beakers, the scoopula, or the sodium thiosulphate pentahydrate.
we didn't take note of the temperature cause we used a computer
we used a temperature probe
yes. we did wait an extra 5 degrees i made a mistake on the excel sheet
explain what the air jacket is
200 OR 150 ml of water i need to check
we used a 250 mL beaker....
observations/data/calculations (I'm doing this part. DID YOU KNOW WE HAVE 30 MINUTES OF DATA?)
error (some i thought of)
the computer program could only have graphs up to five minutes so there was a lag between each graph approx 29 seconds each...as a result those results we obtained through simple math and averages....
time lag of transferring to air jacker
hard to deteremine if all of the sodium thiosulpahte had liquified (this might be human. hm unsure)
thermoter only had to .1 decimal. not very accurate.
okay...here are links to our data.